Originally Posted by
RobertS975
I have made overlapping reservations many times without issues. There is no rule that says you must be certain which trip you are taking.
From the CoC:
E) Fictitious Bookings
Multiple bookings of a fictitious nature are prohibited by Delta. In the event Delta determines that an individual has confirmed such bookings to one or more destination(s) on or about the same date(s), the carrier reserves the right to cancel all confirmed space associated with the multiple reservations without notice to the passenger or the person making the booking.
And they do run sweeps to kick out duplicate or overlapping bookings.